1. Field of the Invention
This invention relates to cooling systems of the type especially adapted for use in connection with internal combustion engines.
More particularly, the present invention relates to pressurized cooling systems through which a liquid coolant in circulated.
In a further and more particular aspect, the present invention concerns improvements for continuously maintaining a volume of coolant within the system.
2. The Prior Art
To maintain temperatures within safe limits, internal combustion engines are commonly provided with a pressurized liquid cooling system. Within the system, heat is absorbed from the engine and transferred for dissipation to the atmosphere. Liquid coolant, circulated within the closed circuit of the system, functions as the heat transfer medium.
Briefly, as will be readily appreciated by those skilled in the art, the system includes a water jacket encompassing the combustion chambers in which heat is generated as a result of the combustion of fuel. Terminating at respective ends with an inlet and an outlet, the jacket weaves a generally circuitous path within the engine. Typically, the outlet resides proximate the top of the engine while the inlet is located at a lower elevation.
A radiator, the heat dissipation component in the system, usually resides at a location spaced forwardly of the engine. Generally fabricated of relatively thin walled material, the radiator includes a core positioned between an inlet tank and an outlet tank. Functioning as a heat exchanger, the core serves to lower the temperature of the coolant flowing from the inlet tank to the outlet tank.
The inlet tank is provided with an inlet port. An outlet port is integral with the outlet tank. A supply conduit communicates between the outlet port of the outlet tank and the inlet port of the water jacket. Communicating between the outlet port of the water jacket and the inlet port of the inlet tank is a return conduit. The return conduit and the supply conduit are colloquially referred to as the upper radiator hose and the lower radiator hose, respectively.
Circulation of coolant within the system is effected by a pump having an intake port and a discharge port. Commonly referred as a water pump, the device is generally affixed to the engine with the discharge port in direct communication with the inlet port of the water jacket. Hence, the intake port functions as the inlet for the water jacket and receives the supply conduit extending from the outlet tank. In accordance with conventional technique, a fan for drawing a stream of air through the core of the radiator, is carried rearwardly of the radiator.
The conventional cooling system further includes a tubular member, dubbed the filler neck as a result of originally intended purpose. Extending from the inlet tank, the filler neck terminates with an open end encircled by an outwardly directed annular ledge and a depending circumferential skirt. Spaced from the open end is an inwardly directed annular ledge which functions as a valve seat. Intermediate the open end and the valve seat is an overflow vent, usually a radially projecting nipple.
A closure and valving apparatus, commonly referred to as a radiator cap, is detachably securable to the free end of the filler neck. The apparatus includes a cover which is extendable over the open end of the filler neck and carries engagement means which are detachably engagable with the engagement receiving means carried by the skirt. A valving assembly, usually including a pressure valve and a vent valve, are carried by the cover. The typical pressure valve includes a depending spring bearing against a disk-like member supporting an annular gasket. The disk-like member may also support the normally closed vent valve.
As a result of the configuration of the engagement means and the engagement receiving means, the cover is rotatable relative the filler neck between a removal position, an unlock position, and a lock position. Normally, the system functions with the cover in the lock position. As a result of the force of the spring, usually a coiled compression spring, the gasket is held in sealing engagement with the valve seat. In the unlock position, the gasket is spaced from the valve seat and fluid communication is established between the inlet tank and the overflow vent. The closure and valving apparatus is separable from the filler neck in the removal position.
It is common knowledge that for optimum operation the temperature of an internal combustion engine must be elevated above ambient. It is equally well-known that contemporary internal combustion engines are capable of operation at temperatures substantially above the normal boiling point of water. With judicious selection of coolant and proper choice of pressure valve, a pressurized liquid cooling system is compatible with such conditions of operation. For example, a coolant comprising fifty percent water and fifty percent ethylene glycol used in combination with a pressure valve having a compression spring exerting fifteen pounds of pressure will provide a system in which the boiling point is raised to approximately 271.degree. Fahrenheit. Even at normal operating temperatures, however, the coolant expands in response to absorption of heat. In a properly functioning system, thermal expansion is usually in the range of three to five percent. Considering a system having a nominal capacity of 16 quarts, five percent expansion increases the volume of coolant by 25.6 ounces or 0.8 quarts.
Assuming the system is filled to capacity, the expanding coolant will counteract the spring and unseat the valve allowing the excess coolant to escape through the overflow vent. Upon cooling, generally after cessation of operation of the engine, the coolant contracts creating a potential vacuum within the system. In response thereto, the vent valve opens allowing make-up fluid to enter the cooling system.
Originally, the coolant overflow containing expensive anti-freeze was lost, having been discharged to fall upon the ground. Air became the naturally occurring make-up fluid. It was periodically necessary, therefore, that motorists remove the radiator cap and add make-up liquid, usually water.
During the relatively recent past, a solution to the foregoing problem was devised. The remedying apparatus included a container or overflow reservoir positioned within the engine compartment remote from the radiator. An overflow conduit communicated between the bottom of the container and the overflow vent of the filler neck. The coolant overflow was discharged into the reservoir where it was held and subsequently returned to the cooling system during cool-down. A vent, open to the atmosphere, prevented bursting or collapsing of the container during respective cycles of the cooling system. The remedy, which achieved substantial commercial success, became know as "Coolant Recovery System". With the advent of the coolant recovery system, came an awareness of the effect of air within the cooling system. Although not universally understood nor appreciated by practitioners in the art, air within the cooling system is extremely deleterious. The presence of air, a heat transfer medium vastly inferior to liquids such as water and anti-freeze, materially reduces cooling system efficiency. Among the system deteriorating effects, air is responsible for cavitation of the water pump, corrosion of the water jacket, and oxidation of radiator hoses. As a statistical example, it can be shown that the presence of five percent air will reduce maximum system pressure by approximately fifty percent.
The coolant recovery system addressed the problem of air within the system. Use was made of the phenomenon that any free air within the system will rise to the top of the inlet tank. Coolant, rising as a result of thermal expansion, will displace the air which will be forced out through the vent and the conduit into the overflow reservoir. In reality, most air will be purged in a foamy or vaporous combination with coolant. Depending upon the heat buildup, a quantity of coolant will follow the air and the vaporous combination into the reservoir.
As the overflowed vapor or foam condenses within the reservoir, the entrained air effervesces upwardly and escapes through the vent into the atmosphere. The deaerated coolant settles to the bottom of the reservoir. As the system cools, only the deaerated coolant will be siphoned back through the vent valve.
To complement the function of the coolant recovery system, companion developments were made regarding the radiator cap. The ameliorated cap design positively prevented communication between the cooling system, except for the atmospheric vent in the overflow reservoir, and the atmosphere. Motorists were instructed to maintain a reserve supply of coolant within the overflow reservoir. To retard evaporation and entrance of air into the system, the radiator cap was removed, if ever, only when the system was cool. Periodic replenishment was accommodated through an opening in the reservoir.
Despite unparalleled advancement to the art and international acceptance, the coolant recovery system has not been an optimum solution. Being vented to the atmosphere, coolant evaporated from the overflow reservoir. Another quantity of coolant was lost along with the escaping vaporous combination of air and coolant. Further, inattentive motorists frequently neglected to maintain a necessary minimum level of coolant within the reservoir.
More importantly, however, the coolant recovery system is dependent upon cyclic heat and cooling of the engine. Air is expelled from the cooling system only during heating and coolant is returned only during cooling. Inspection and attention of the fluid within the system was limited to the vehicle being at rest with a cool engine. Replenishment of coolant, as may be necessary to accommodate a leak within the cooling system, was not possible.
The prior art has provided a purported solution to the foregoing problems. One solution was the provision of a combination radiator/automatic positive anti-aeration system in which the components were assembled to function cooperatively as integral units in which external plumbing is either entirely eliminated or reduced to a minimum. For retrofit to a preexising vehicle, however, the modifications required that the radiator be removed from the vehicle, physically disassembled, reduced in width, reassembled, and reinstalled in the vehicle. The substantial expense of such a modification and the adverse effect on cooling system performance made the system less than an optimum solution.
The prior art has also made attempts to warn the motorist of an imminent overtemperature condition as a result of low coolant level. Proposed was a pencil-like probe which was inserted into the radiator header tank through an especially created aperture. An hermetic seal was established between the aperture in the radiator header tank and the coolant sensor probe by a complex seal assembly which including a threaded fitting, washers and various sealing devices. The device, however, failed to alert a vehicle driver until after the volume of circulating coolant had decreased to a critical level. Further, the probe was eventually rendered useless as the result of an accumulated coating of deposits of material normally held in suspension within the coolant.
It would be highly advantageous, therefore, to remedy the foregoing and other deficiencies inherent in the prior art.
Accordingly, it is an object of the present invention to provide improvements in pressurized liquid cooling systems of the type normally used in connection with internal combustion engines.
Another object of the invention is the provision of increasing the effective capacity of a liquid cooling system by making available to the system, during engine operation, a reserve supply of coolant held in an accumulator.
Another object of the invention is to provide means for deaerating and receiving overflow from a pressurized liquid cooling system and making the overflow available for return to the system while the engine is in operation.
Still another object of the present invention is the provision of improvements whereby the condition and character of the coolant may be examined when the engine is hot.
Yet another object of the invention is to provide an automatically refillable engine coolant system which provides a sensible warning of a coolant loss condition.
Yet still another object of this invention is the provision of means for cooling and condensing overflow coolant before being received within the accumulator.
And a further object of the invention is to provide means to retard evaporation of liquid from the reserve supply.
And a further object of the instant invention is the provision of improvements for more expeditiously purging air from the pressurized liquid cooling system of an internal combustion engine.
Yet a further object of the invention is to provide improvements of the foregoing character which may comprise a kit for retrofit to a preexisting conventional cooling system.
And still a further object of the invention is the provision of relatively inexpensive improvements which are readily and conveniently installed with common tools and without modification to the existing hardware.